This invention relates generally to an electrostatographic printer and copier, and more particularly, to a segmented drive roll for an exit nip prior to the exit trays.
In high speed copiers, the process speed of the paper at the exit nip of the purge and sample trays, or all exit trays in general, is too fast to achieve acceptable stacking.
Two methods currently used to reduce the speed of the paper at the exit nip both rely on sensing when the trail edge of the paper exits the next to the last nip in the paper path. In the first method, a stepper motor is used to slow the exit nip down after the trail edge of the paper has left the preceding nip. The second method utilizes a solenoid to elevate the idlers of the final nip which is traveling at a lower surface speed than the preceding nip. Just as the trail edge of the sheet is exiting the next to last nip the solenoid releases and drives the sheet out at reduced speed. Both of these methods involve complexities that result in significant UMCs (unit manufacturing costs). In the first method, the stepper motor method requires the expense of both the stepper motor and a controller board, and when combined with the extensive development time necessary, adds significant expense to the final cost of the machine. In the second method, using the solenoid is not as costly as the stepper method, but still requires complex mechanisms to lift the idler shaft, which adds to the UMC. In addition, the solenoid method requires a large area in the machine for mounting the hardware, which sometimes is not available. In both situations, software must be present which senses the trail edge of the sheet to signal the stepper motor or solenoid to take the appropriate action.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
Application Ser. No. 08/583,907, filed Jan. 11, 1996, to Rider et al., discloses an apparatus and method that describes utilizing a corrugation slip nip system, including a variable force idler that encompasses three stages, to prevent buckling of print media traveling at a high rate of speed upon exiting from a high speed printing machine to the exit tray for stacking. Buckling concerns are eliminated by allowing the sheet, driven by a high speed positive drive nip, to slip through the slower speed corrugation nip, yet still having enough drive force in the slip nip to drive the sheet into the exit tray. In order to vary the normal force on the sheet, a three stage variable force idler is used. The first stage oversizes the inner diameter of the idler rollers on the idler shaft. The second stage uses a slot in the spring which allows the idler shaft to move upward without deflecting the spring. These first two stages are particularly adapted for light weight paper. The third stage occurs when the idler shaft is topped out in the shaft slot such that the paper deflects the spring causing additional force to be applied to the paper to drive the paper out of the system and into the exit tray. The third stage is reached only where heavy weight paper is used because heavy weight paper has sufficient beam strength to deflect the spring.
U.S. Pat. No. 4,124,204 to VanBushkirk discloses an improved sorting apparatus and reproducing machine provided with a plurality of sheet receiving bins. A first frame supports the bins. A sheet transport is arranged in a second frame. The frames are supported for relative movement between a first closed position wherein the sheet transport is operatively associated with the bins and a second open position wherein the sheet transport is operatively associated with the bins and a second open position wherein access is provided to the transport and bins for sheet clearance. The sheet transport includes at least one belt which is operatively maintained under a desired tension. A device is provided for reducing the belt tension in response to the relative movement of the frames between their respective closed and open positions. In accordance with another feature, a counterbalance is provided for counterbalancing the frame supporting the transport as it moves away from the frame supporting the bins. The counterbalance comprises at least one type device mounted to the transport frame which engages the cantilever spring.